RobLe

Solar thermal is unusual these days - a pro install is expensive for what it gives you, compared to solar electric. Loads of hot water in summer, nothing in winter. I appreciate you get the same summer glut with PV - but at least you can sell it to the grid and it serves a purpose replacing fossil fuel use elsewhere. ST does lend itself to diy install much more than PV - there's no regulation on it, and diy keeps the cost down making it more attractive. Good luck whichever way you go!

The pipes should be insulated, so you’d not expect much condensation. They shouldn’t have dips in them for puddles to form. And that air is on the way out, it’s not coming back in ever!

I suggest each cable has its own appropriate mcb rather than paralleling both ends - perhaps a 16A and 24A mcb, although the sparky should be choosing and fitting this sort of stuff. Nb there shouldn’t be an RCD involved unless it’s the expensive dc capable type.

Our Vent Axia Sentinel Kinetic had a puddle in it some 6 or 7 years ago. It was weird - like the drain was blocked with some biological thing. Anyway, I unclogged it as best I could, and plumbed in the other drain (there are two, front and back) as well. Haven't had a problem since. We also had problems with the drain icing up, as originally I had it dripping outside onto a flat roof - it iced up, blocked, and leaked inside, there must have been over 10litres of water all told into the loft, it made a stain on a bedroom ceiling. The drain is plumbed into the bath drain now, which doesn't go outside so doesn't cause a problem.

I shall assume that the condensation is on the inside, in which case I suggest that you get a decent temperature and humidity meter, and ideally CO2 (not CO) as well - £50 will get this. What’s the window frame construction, photo? Most likely (jumping the gun on your answers) is that the RH is high and window is old school U=2.7 so two pronged attack would fix: replace glass and drop RH. If RH high but CO2 low (unlikely) then dehumidify; usually CO2 is also high, so you really should ventilate more - MVHR is the gold standard soln for this, other solutions are available🙂.

Our home was built in 1963, brick outer block work inner with a cavity. Went with glass wool instead of eps due to mains cable wiring found routed in the cavity. Eps may slowly leach out the plasticiser in pvc cables leaving them brittle - it’s why cables come wrapped in plastic if they are near polystyrene packaging. This was 20 years ago; now we’ve got EWI as well, which is excellent! When the house was being EWI’d I found (and fixed) CWI was missing in a few places - under windowsills, tops of cavities, behind upvc cladding (there’s still a cavity wall behind there).

Interesting idea! I think you’d need lots of them- if you had just one pair, and one thermosiphon, then I think the theoretical best efficiency will be 50%. Often mvhr have hexagon shaped cores (well ours does), so that a lot of the heat exchanger is counter flow rather than cross flow, as this improves efficiency - like the pic below. The HX is best made with many sheets of thin plastic spaced a couple of mm apart, more total area gives better efficiency. CO2 controlled fans are a massive efficiency improvement - you could do this with/without the HX. There are simple ones with 0-10V o/p available from digikey.

We're likely to sell our V2H unit at some point. It's always worked fine for us, it's got several settings available on the Indra Portal - unfortunately I think this portal is only available in the trial and I doubt you could persuade them to allow it off grid - they don't generally even offer 2nd hand unit support. I think the unit will carry on working in that mode; but it might want to "phone home" at some point - it normally connects over the internet. I've tried it several times without the internet - I've never known it not work like that, but it may get upset eventually, who knows. The most likely useful setting for Square Feet would be "Load match" the whole time - with a CT on a grid forming inverter, then the car will push or pull up to 4kW (it is a 6kW unit, ours is locked to 4kW for dno reasons) in or out of a grid forming hybrid inverter system. Eg a Sunsynk inverter + battery system creating a grid, the car bolstering it if there - Sunsynk could then manually be triggered to pull power from the car. While I can't see why it wouldn't work, until somebody tried you'd never be sure the inverters didn't get upset. The grid forming stuff would cost anything from rock bottom £6k (3.6kW + 15kWh(see Seplos Mason EVE 280 kits) + 4kWp PV, all DIY) upwards - personally if space I'd go for a bigger unit and loads more PV. You can always parallel up Sunsynks - other inverters are available. As suggested above, a genny would get you out of trouble!

I have some experience in a few areas here: We have a Nissan leaf, been on the OVO V2G Indra trial for 3 years, and now a V2H trial for 1 year. You could indeed charge the car up elsewhere, and then run it as V2H back at home to bolster a home battery. The Indra V2H box does not generate a grid - it has a CT clamp which it nulls by pushing in more power to an existing grid. So with our V2H box & a Nissan leaf you'd need a home battery system which was islanding to generate the local grid in the first place. When the car is connected, this home batt system can be programmed to pull power in, and the car will oblige if it can, to top it up. We have an elec only home which is almost enerphit, with a 2.5kW gshp providing heating and DHW. There's 4 people living there, with "normal" lifestyles, so using 3500kWh/year(stuff) + 2000kWh/year(heating+DHW) + 1500kWh/year(elec car going places) - 3600kWh/year(PV). My only issue with what you want is that modern lifestyles amounts to a lot of power; maybe you are more frugal - that would make it much easier! We do have 4kWp of PV, so we could be self sufficient in summer, but definitely not in winter - for us, a cold winters day would consume 10kWh(stuff.. telly/fridge/laptops..modern stuff...) + 10kWh(heating+DHW) + 4kWh (car) - 2kWh(PV). So we import 22kWh for the day - which is probably more than our old 30kWh Leaf can fit in it these days. An honest appraisal of your energy demand is needed I think. Good luck!

Double glazing should have a dry inert atmosphere in the gap. Secondary glazing is best I think with an air gap which ideally comprises of outside air. It's not generally done this way - 2ndary is normally aftermarket added onto the inside, so likely to dominantly have high absolute humidity indoor air in the gap that may condense on the outer pane in winter. So it will suffer less from condensation if the original windows are a bit leaky, and the new added 2ndary stuff is well fitting.

I’ve had a failed can similarly. I assume if it’s stored upright then maybe gas can slowly creep out. Ive taken to storing it slightly upside down, thinking that the gas will force out a bit of the foam which will self seal rather than leak the contents.

I think there will be resistance to swapping from gas to heatpumps in the new build sector. Gas boilers are generally massively oversized as there is no cost penalty for this - and right now this allows shoddy building practices to go un-noticed. Fit a correct-to-the-design heatpump instead - and it will be evident if the building is substandard - eg. missing insulation / gaps between sheets in the cavity / air leaks etc.

I think it’s not so much the home-owner issue. R290 has been resisted due to more complex manufacturing and maintainance, and probably lobbying by the fgas industry to keep the means to their privilege. There are rules for R290 charge levels indoors so that in the worst case scenario it still can’t explode. Yet ‘natural’ gas is still actually piped into almost every home in the UK !

That’s not true - R290 (propane) is just about as good as you get for a refrigerant. It was shunned for years because it’s flammable, not for performance reasons. All else being equal, if you’re manufacturing or maintaining a heatpump, you’d prefer a gas that isn’t explosive. Unfortunately there’s no perfect gas - they all have downsides - ozone depletion/global warming/flammable/toxic/very high pressure needed. Propane (HC in graph below), ammonia, CO2 were used 100 years ago, and are coming back after a while with CFCs :

Our 240l tank runs for 3 hours in the ‘go’ period overnight, it usually just gets to 50C, then stops heating. It’s enough for us, never runs out (2 adults, 2 teenagers, nobody takes super long showers). It’s a 2.5kW gshp. We have PV, but our export is close enough to the ‘go’ import price - so I figure it’s both more reliable to run on go power than PV (what if it’s overcast?) and it’s greener anyway to export elec when it’s needed more.

It’s all sorted out now, Octopus have finally given in! I’ve not done anything, other than email again and again and again, and now the SEG is going. I can only assume the person I was emailing didn’t know what was allowed/not allowed - he finally gave in after I found and sent snips from Ofgem and Octopus which backed me up. I think it took a long time as he sometimes mixed up export and generation when he talked about FIT, and talked about the ‘register’ without saying what it was. Anyway, we now get FIT generation and measured SEG export, all good.

Digikey looks like they sell the similar Panasonic U-vacua. Please check my maths - I think the largest 610mm by 610mm by 25mm thick panel (link below) at £53 each is equivalent to about 125mm of celotex. So it’s much better performing than an aerogel blanket(which only just beats celotex), but pricey for a whole house - and don’t hammer in any nails! I think these panels are actually used in high end fridge freezers. https://www.digikey.co.uk/en/products/detail/panasonic-industrial-devices-fbd/CNRZZB78400/9558502

LiFePo4 cells are 5kg per kWh; how heavy would this suitcase be ?

ICE cars generally run a compressor mechanically from some rotating engine part, with a rotating "seal". Regular heatpumps have actual seals, or welds. Our old ICE car a/c never worked when we got it at around 5 yr old sadly. Tried to regas it once, didn't last long. 14 yr old Mondeo. One day we will ditch it and the leaf and get a long distance BEV with a/c, joy.

Ha! Maybe I'd think differently if I got close to that. We don't; we would've been better off financially if the meter wound back instead. The old meter would've avoided a load of paperwork hassle. It would stop iboost during the day stuff. It would prevent charging batteries during the day, using them at night - plenty of people do this still, as they don't get paid to export. In general, it would better align the individuals finances with what's best for the country. I'm an engineer - I should be greatful for all the jobs for my mates designing the stuff that ties me in knots I guess.

I'm having difficulty with the whole FIT and SEG thing now. The history is: 4kW PV on FIT in 2012 from good energy Nissan Leaf V2G trial in 2020 with OVO, smart meter fitted. FIT deemed exports stopped, (FIT generation same, still good energy), metered exports started. After the V2G trial, we swapped to Octopus - been with them a year - but haven't yet managed to get anything for export. The car now does V2H, although I expect it will end up bricked (software locked) eventually. I'm in email conversation with Octopus, but no joy so far. Both Octopus and Ofgem state that you can simultaneously receive SEG export and FIT generation (but not export) - I think "export" and "generation" has been repeatedly confused by them, so they have written incorrectly things like "please note that you are not able to receive FIT Generation payments as well as export credit from us simultaneously" - I think this is now sorted. Now I have been asked for "proof that Good Energy have removed your account from the register" - which opens up so many questions in my mind! What is this "register"? Can Octopus not see it ? If it is the "FIT database", then I cannot see it as an individual. I have previously copied emails from Good energy to them which state that we receive no FIT export - is this not enough? What would constitute proof that I have access too? I've asked for a screenshot indicting "the problem", but GDPR prevents it, gahh! Anyway, they seem to keep responding, and I am politely plodding away. It just seems a waste of time for all concerned. I would swap all the FIT and SEG and Smart meter rubbish in a heartbeat for the older mechanical meter that could just wind back on export.

We haven’t got a buffer tank. Just a simple old radiator system - none of the downstairs radiators have TRVs so that there’s always a big enough water volume and thermal load.

A cop of 2.5 is fine for dhw, although it’s a fair amount of total heat used. Do you need to reheat the tank so often? There’s a lot of pipe and tank loss from dhw heating. We heat ours just once a night, in the cheap slot electric. Space heating is a poor cop, likely indicating your rads are running hot. What is the heating flow temperature (I’m guessing the installers set it high). In the ideal world when you touch a rad you can barely tell it’s on, ours run at 32C.

Eco eye data logger? Been around a while, you can pick up 2nd hand ones for £25. Logs to sd card. Measures current, and capacitively voltage - so you get power factor correctly but it doesn’t know the actual voltage. https://m.facebook.com/marketplace/item/1402792330508024/?ref=search

I'd recommend MID certified 3rd party metering, with a bare minimum being a cheap inline MID certified elec meter. I'd never trust the manufacturers data. I'd be too concerned they "guessed" sometimes, or failed to include pumps, fans, etc. Glad to hear you might be getting a heatpump sorted!